Refactor - Separates the text section from read-only sections

[Lichtso]

Preparation so that the strict ELF parser can enforce a clear layout in which text and read-only sections are separate.

This PR removes the indirection in which the text section is retrieved from the possibly concatenated read-only sections. There is only ever one text-section and no need to concatenate it. So instead the text section can be borrowed as a sub-slice of the relocated ELF bytes directly. Also removes the mem_size of text_section_info as that was double counted and the debug name, as it was unused.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.11765% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 89.47%. Comparing base (179a0f9) to head (63188cf).

❗ Current head 63188cf differs from pull request most recent head 7fcd282. Consider uploading reports for the commit 7fcd282 to get more accurate results

Files	Patch %	Lines
src/elf.rs	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #553      +/-   ##
==========================================
+ Coverage   88.34%   89.47%   +1.12%     
==========================================
  Files          24       23       -1     
  Lines       10282     9911     -371     
==========================================
- Hits         9084     8868     -216     
+ Misses       1198     1043     -155     

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[alessandrod]

There is only ever one text-section and no need to concatenate it

I haven't looked at the change yet but this is not true?

[Lichtso]

There is only ever one text-section and no need to concatenate it

We only consider the byte range of one section:

rbpf/src/elf.rs

Line 415 in 179a0f9

offset_range: text_section.file_range().unwrap_or_default(),

which is exactly named ".text":

rbpf/src/elf.rs

Line 396 in 179a0f9

let text_section = elf.section(b".text")?;